This invention relates to a mobile material handling apparatus which comprises a frame, an input arrangement for receiving a bulk supply of raw material to be handled, means mounted on the frame to transfer material from the input arrangement to a discharge arrangement, and a wheel set supporting the frame to render the apparatus mobile.
A material handling apparatus according to the invention has been developed primarily (though not exclusively) in connection with the processing of a bulk supply of material which requires to be separated or xe2x80x9cscreenedxe2x80x9d into at least two separate portions or fractions. The separate portions could comprise undesired material on the one hand, and one (or more) screened portions of desired material in a predetermined size range. Alternatively, all of the bulk supply of raw material could be desired material, and the function of the apparatus then is to screen the raw material into two or more different size ranges.
However, while the invention is particularly applicable to a material processing equipment (in which the xe2x80x9cprocessingxe2x80x9d can include crushing and/or shredding of the bulk supply of raw material and/or screening of the material into one or more size range), the invention also contemplates simpler type of mobile material handling apparatus, and which has an input arrangement to receive a bulk supply of raw material, a discharge arrangement, and one or more conveyor or transfer means to transfer the material between the input and the discharge arrangement.
In a stone quarry installation, it is known to use a large screening plant, which receives a crushed supply of rock material and which separates the material into different size ranges, and then discharges the screened material to separate discharge points to form progressively increasing stockpiles of material.
In some installations, a screening plant is a substantially permanent fixture, and which is assembled on site, but which is not capable of being rapidly dismantled on site for subsequent transport to another site and subsequent re-erection. Therefore, although in theory a so-called permanent screening plant could be dismantled, transported onto a low loader to another site and then re-erected, in practice this generally does not happen. Furthermore, on a particularly large quarry site, it may be desirable to move a screening plant from one place to another as quarrying proceeds, and permanent screening plant fixtures cannot be utilised to meet this potential need.
Accordingly, to provide a facility for screening plant to be moved from one site to another (including transport along the public highway), or to be moved a short distance on any particular site, it is known to provide mobile screening plants with at least one wheel set to support part of the frame of the plant, and which can be converted fairly quickly between an operative (screening) mode and a transport mode. Given the fact that screening plants generally are of substantial overall size, and typically have a number of lengthy transfer conveyors to transfer material from one processing and/or handling device to another, and also usually have laterally projecting discharge conveyors to form separate stockpiles alongside the plant, considerable ingenuity is required in designing the components of the plant, so as to make it a relatively straightforward and non-skilled, and also rapid task to convert the plant components between operative (deployed) positions and transport positions.
Reference may be had, by way of example only, to known designs of mobile material processing plant, as disclosed in EP 0506812, EP 0407549, EP0726818 and EP 0301798.
Upon conversion of existing designs of mobile plant to a transport mode, it is usual for the forward end of the plant to be mounted on a low loader, or on a fifth wheel coupling, and the remainder of the plant then can be towed along the public highway, utilising one or more wheel set which supports the remainder of the frame of the plant. However, while this is satisfactory in moving a plant substantial distances from one quarry site to another, it is not suitable for small movement within an existing quarry site, and especially when turning space is restricted, or there is little free space available for manoeuvre.
The present invention has therefore been developed primarily with a view to provide improved manoeuvrability on site to a mobile material handling apparatus of a type which is capable of being converted readily to a transport mode for being towed along the public highway a substantial distance from one site to another.
According to the invention there is provided a mobile material handling apparatus which comprises a frame, an input arrangement for receiving a bulk supply of raw material to be handled, means to transfer the material from the input arrangement to a discharge arrangement, and a wheel set supporting the frame to render the apparatus mobile; in which a set of endless tracks is mounted on the frame and which is adjustable between an inoperative condition out of contact with the ground and an operative ground-engaging position when it is required to manoeuvre the apparatus on site.
The wheel set supports part of the frame of the apparatus, and allows the apparatus to be manoeuvred through small distances on site when the set of endless tracks is adjusted to the operative condition. However, when the track set is adjusted to the inoperative condition, the frame of the apparatus may have additional ground support e.g. additional support legs, which allow the apparatus to carry out required material handling operations at a particular position on site. However, when it is required to transport the apparatus a substantial distance from one site to another, the frame of the apparatus may be coupled to a low loader or a fifth wheel coupling, to enable the apparatus to be towed like a trailer with the wheel set supporting the remainder of the frame (and with the set of endless tracks adjusted to the inoperative condition).
The endless track set may be movably mounted on the frame to be adjusted between a raised inoperative position, and a lowered operative position.
In order to assist the manoeuvrability of the apparatus, it is preferred that the frame of the endless track set is connected to the frame of the apparatus via a swivel mounting e.g. a centrally located pivot on the frame of the endless track set.
The input arrangement may comprise a simple supply chute or hopper to receive a bulk supply of raw material, and a conveyor may run from the input arrangement to a screen box which screens the material into different size range(s), the or each of which can be discharged via a respective discharge conveyor, which is preferably adjustable between a folded transport position, and an outwardly extending or deployed operative position.
The input arrangement may include a preliminary screening function e.g. to discharge undesired material. such as tree roots and branches, or rubble, if the raw material supply is site clearance material.
The input arrangement may also include a crusher and/or shredder machine to carry out required material processing action, prior to screening equipment.
A preferred embodiment of mobile material handling apparatus will now be described in detail, by way of example only, with reference to the accompanying drawings.